The present invention relates to a chemical vapor processing method for depositing or etching a film on a plurality of substrates.
Thin films of non-single crystalline semiconductor have been deposited on a substrate by chemical vapor deposition (hereafter CVD). Such films made of silicon oxide or silicon nitride are suitable for thin film transistors which are used for photoelectric conversion devices such as solar cells, image sensors and the like, or driving devices for liquid crystal devices.
Referring to FIG. 1, a prior art CVD apparatus is schematically illustrated in part. In the figure, the apparatus is formed with a plurality of reaction chambers 2 and 3 and a loading chamber for inputting a substrate into the reaction chamber 2. The substrate 11 is mounted on a substrate holder 10 and transported together with the holder. Each reaction chamber is provided with a heater 6 and a pair of electrodes 4 and 6, the heater 6 functioning also as the electrode. The substrate is heated to a predetermined temperature by the heater 6 and coated with a film by chemical vapor reaction by means of discharge taking place between the electrodes 4 and 6.
As apparent from the figure, the electrode area must be enlarged, if coating on a larger substrate is desired, because the substrates 11 are arranged in parallel with the electrodes. In this process, the coating area of the substrate is limited to the corresponding area of the electrodes.
In order to resolve the conventional shortcomings, another type of deposition system has been proposed in Japanese Patent Application No. sho59-79623 of the Applicant. A plurality of substrates can be treated in this system by arranging the substrates perpendicular to a pair of electrodes inbetween as shown in FIG. 2. Although this proposal is excellent in handling many substrates at once, deposited films thus produced are uneven. In particular, the thickness of the film depends on the distance from the electrodes.
For this reason, uniform etching cannot be accomplished with the prior art device.